Nozzle for removing adherent materials



Aug. 14, 1955 H. A. LANDE NOZZLE FOR REMOVING ADHERENT MATERIALS Filed Del 5. 1952 :s @u E INVENTOR nl i n United States Patent O N OZZLE FR REMOVING ADHERENT MATERIALS Homer A.. Lande, Marion, Ind., assigner te Radio Corporation of America, a corporation ot Delaware Application December, 1952, Serial No. 323,755 'l Claim. (Cl. 51--1'1) This invention relates to cathode rayv tubes and particularly to apparatus for removing tluorescent materials from viewing screens of such tubes. t

A cathode ray tube is one having an elongated envelope with an electrode structure or electron gun at one end for forming a cathode ray beam which is focused and scanned over a lluorescent screen at the other end of the envelope to produce an image or picture thereon. Such a iluorescent screen may comprise blue tuorescing zinc sulfide and yellow iluorescing zinc cadmium sulfide in the desired proportions to provide a white luminescence, for example. In the manufacture of the tube, the phosphors are mixed with other materials, such as a water soluble silicate binder, for example, which facilitate settling the phosphors on and their adherence to the glass face plate of the cathode ray tube.

During the manufacture of cathode ray tubes, a substantial number of tubes are rejected as failing to meet certain standards of performance. Since the tube components, especially the tube envelope, are costly, an effort is made to salvage parts which may be re-processed and used in other tubes. In the case of the tube envelope, re-processing usually involves removal of the uorescent materials or phosphors from the viewing screen or face plate of the tube.

In the past, fluorescent vmaterials have been removed from cathode ray tubes by means of acid solutions. This method has proven satisfactory for use with glass cathode ray tubes (or kinescopes, as television picture tubes are usually called) and some metal tubes. However, the present trend is to construct the metal envelopes of'kinescopes of cold rolled steel, which is much cheaper than the high chrome steels now used for that purpose. The use of cold rolled steel in the cone of the tube requires that a glass having a highkcoeicient of thermal expansion be used for the face plate and the glass neck of the.

tube. Both the glass and cold rolled steel are by their nature characterized by poor resistance to chemical attack, so use of acids as a means for removing phosphor` materials cannot be used in this case.

Another disadvantage of using acid to remove fluorescent materials from screens is that chemical reactions' take place with the phosphors as well as the wanted reaction with the silicate which is used to make the screen adhere to the face plate. Consequently, the phosphors thus removed are wasted, because the cost of salvaging the phosphor and reclaiming it is more than the cost of preparing new'phosphors. Additional disadvantages of acid removal of screens are that toxic by-products may be produced by chemical reaction between acid and the phosphors, and the fact that the acid itself is rather costly.

A principal object of the present invention is to provide an improved means for removing uorescent screens from cathode ray tubes. f

A further object of the present invention is to provide a means for removing phosphors from a cathode ray tube in a readily salvageable form. Another object of the present inventionr is to provide 2,758,423 Patented Aug. 14, 1956 ice a means for removing iluorescent screens from kinescope faceplates which is free from the dangers of toxicity which were inherent in the prior art method.

Yet another object of the present invention is to provide a novel and more economic means for removing screens from cathode ray tubes.

The above and related objects areaccomplished 'in accordance with the present invention by directing a high velocity rotating air mass towards the phosphor screen. The high velocity of the rotating air mass, which resembles a miniature hurricane, insuresk a mutual friction force between the air mass and phosphor particles which is of sucient magnitude to overcome the adhesive and cohesive particles formed by the binding substances incorporated within the screen.

A novel type of non-rotating nozzle or jet head, hereafter referred to as the airoten which is inserted through the neck of the tube, contains tangential orifices which, when high velocity air is released therethrough, sets up the rotating air mass. Because the rotating air mass, like a hurricane, has a relative calm center or eye, it would be ineiiicient in removing the phosphors at the central portion of the screen. Therefore, to insure removal of the phosphors over the entire screen, the airoter is provided with an additional orice lthrough which air is directed towards the center of the face plate, thus dislodging phosphor particles which otherwise would adhere in that region.

The compressed air which is used in the practice of the present invention may be produced much more cheaply than the hydrofluoric acid formerly yused to remove fluorescent screens. Additional savings, brought about by a reduction of the time spent in washing the tube envelope after screen removal, may also be realized. While air is the gas referred to in the description of the present invention, other gases could be used, especially if air would cause excess oxidation of parts.

Referring to the accompanying drawings:

Fig. l is an elevational view of apparatus which may be employed in the practive of the method of the present invention, a part of said apparatus being inserted within a cathode ray tube envelope from which the fluorescent screen is to be removed;

Fig. 2 is an enlarged plan View, in section, of the nozzle shown in Fig. 1, and taken along the lines 2 2 of Fig. 3,

Fig. 3 is an elevational view, in section, taken along lines 3 3 of Fig. 2.

Referring to Fig. 1, there 'is shown an enclosed table 10 having an aperture 12 in its top 14 which is shaped to hold a cathode ray tube envelope or bulb 16 and center said bulb with respect to an air line 18 and nozzle 20. When the tube envelope 16 is in place on the table'lt), the air line 18 and nozzle 20 extend into the interior of the envelope 16 through the neck 22 of the bulb y16. The air line 18 has a shut-off valve 24 for controlling air llow therethrough, and a novel nozzle or airoter 20 for directing high velocity-high pressure air through tangential oriiices therein to produce a swirling or rotating air mass which loosens and removes the uorescent screen 26 on the face plate 28 of the cathode ray tube envelope 16. The cone v30 of the tube envelope 16 is illustrated as being metal, but may be either metal or glass.

The nozzle or airoter 2G, yshown in detail in Figs. 2

and 3, and which is threaded so that it may be screwed The nozzle 20 has at least one, and, as illustrated in Figs.

Zand '3, has three small tangential, channeled or'itces40 extending from the outer surface of the body 3S into each oftheechannels 34..` `Thecovenplate 42, which closes one end of the central channelz, has a single centrally located apertureor `orifice 44. y

t table rhas alter 46 Aand exhaust means, suchas a fan 48, for removing excess air from the enclosed table 10 iwhile `confining the removedphosphor particles to the enclosure. t Variations in the `physical arrangements and number` of 'the tangential orices may be made to satisfy specific requirements.

Iii theipractice off the present invention,y the bulb 16 fromwhich the `fluorescent screen 26 is to be removed is positioned with its periphery, seated in-the aperture 12" of the tabieiofwith theair line 1s and nozzle or arreter zu inserted through the neck 22 ofvthe tube envelope and extendingl into the interior o f thecone 30. l The valve 24 on the air line `18` is then opened,`and ,high pressure-high velocity air lescapes fromthe vtangential orilices' 40' of the airoter 20 and the single longitudinal oriiice .44. WhenV the air escapes' `from the tangential Aorifices `40, its static pressure isfconverted into a kinetic headand a torque is imposed onthe entire` air mass contained within the bulb or`envelopei16. The torque vthus produced results in the angular acceleration of the entire 'airfmass, and this acceleration continues untilthe air mass `has attained an angular velocity such'that a counter torque, `equal in magnitude to the torque produced by the air leaving the airoter, and

provided by the friction ofthe air mass upon the interior surfaces ofthe bulb assembly and by turbulence within' the air mass, is manifested. The air mass within the bulb thus attains a`constant`"angular velocity the magnitude of which isdependent upon the operating conditions, that is, the airpressure within the airoter 20, the number, length,

and diameter of tangential orifices 40, and the size and form of the bulbor envelope assembly 16. As the air mass gains velocity, it exerts a frictional force upon the phosphor particles adhered to the face plate 2S, and if the operatingconditions are so adjusted as to render the veloci ityof the air masssufiicientlyhigh, the frictional forces exerted upon the phosphor particles will cause them to become'dislodged from `the face plate 28. The rotating air mass may be likened to a miniature hurricanewithin the tube envelopel:

Since the magnitude of the frictional force on the phosphorvparticles by the rotating air mass vat any point varies` directly `with` the linear velocity of the air mass at that point, it is obvious that the linear velocity of theair mass, and thus the frictionalforces exerted bythe air mass, will be insufficient to readily. dislodge the 'phosphor particles in the immediatevicinity of the center `of rotation of the air` mass;l Moreover, since the longitudinal center line'of the'bulb assembly 16' is colinear with the center of rotation of the airmass, and since the longitudinal center line of the bulb ,i assembly `16 intersects the face plate 28atvthe Vgeometriccenter of `the latter, it is evident that phosphor particles atthe centerl of the face plate 28 may beremovedf only with diculty if at all, by the1 rotating air mass alone.

It is for this reason that the airoter 20 is provided with.`

one centrally locatedlongitudinal orifice 44which directs a iet'of high velocity air to the center of theface plate 28, which is at the center or eye ofthe hurricane, thereby disldoging phosphor particles which l mightr otherwise re main adheredvthere.`

Asafspectc example lof how the present invention is practiced, the distance between the nozzleor airoter 20 and thelface plate 28 is-approximately six to eight inches in.1 the. casewof `a 21 inch `metal rectangular tube. For smaller tubes, such1as a17 inch kinescope for example;

this distance shouldrbeV somewhat less thank six to eight. inche'stfor 'optimum'. etliciency in `removing :the screen .26;`

has `l2`fta`n`gential` oritices` (4 banksof orifices) arranged itt Pinwheel fashion, each oriiice'j having; a* diameter? ot4 inch and each bored on 5%,2 inch centers. The perpendicular"distance front" the centerwof the airotcr to the orifices 40 is P/s inch. The effective length of each of the orifices 40 is somewhat in excess of Ms inch. The air pressure within the `airoter 20 is maintained at approximately 70 pounds per square inch gauge pressure, during screen removal. Under these conditions, the uorescent screen 26 will be removed in approximately three seconds. However,`V in actual practice, the `same setup is employed for both 17 and 2l inch tubes, and the distance between airoter 2i)` and the faceplate 28is a compromise between the optimum for eachofthe two tube sizes. Under these conditions, a time cycle of. six` seconds has been found sutiicienttoV insure complete removal of the screen 26 in either size tube.

Following removal of the screen 26, the bulb 16 is subjected to washings with water and in some cases with water, then water plus detergent, and then a final washing with water. Awashing schedule of l5 seconds for each washing'hasbeen found to be'satisfactory, but a substan-` tial variation in the timeschedule would be permissible.

The particles of phosphor which are removed from the face plate 28 (orlother viewing screen surface which may be'inside the tube envelope) function as an abrasive to augment the' frictional action between the rotating air mass-'and thescreen in removingthe phosphors.

"lliisabrasiveaction of the loosened phosphor particles may, if thel distance between the airoter 20I and the face plate 28Vis toot-small', damage theinner surface of the face plate 28? Undersuch conditions the phosphors loosened by the swirling air'mass are thrown into the path of the air escapingfrom the single` longitudinal orice 44 and apparentlycxert an erosive` effect on the 'center region of the tube which is similarto that produced by Sandblasting. However, the` optimum spacing between nozzle 20 and faceplate 28t`or any particular tube size may readily be determined by experiment- The airline 18 should be small enough to provide sufcient'room for the air to escape from the bulb 16, yet large enough to provide suliicient volume of air to accomplish` the desiredresult, `which is eicient removal ofthe screenf26. The table 10 is enclosed to prevent the phosphor particles ejected through the tube neck 22 from beingscatteredl The tilter 46 and exhaust means 481illustrated asbeing'attached to the table'10, remove air and suspended Vphosphor particles from the table 10 and thus maintain near-normal atmosphericpressures within the enclosed table 10.

Whilel airialonerhas proven satisfactory to remove the vast majority of fluorescent screens commonly usedin cathode; way tubes, some screens, particularly screens which may'be aluminizedVare provided with `a highsilicate binder to provide stronger adherence of the screen to the: face plate and thus are more diicult to remove from the face .plate28L With such screens, the addition oiiafwater soluble abrasive` (sodiumcarbonate, for example) to the airsupply willimprove'the eiciency of the screen removal operation.`

The addition of the water soluble abrasive presents no additional problems to the reclaiming of the salvaged phosphors,"` since the phosphors would in any event be washed with water to` dissolvethe silicate type binder used to cause the screen 26 to adhereA to the face plate 28.

lf thephosphors are to be rcprocessed, the enclosed table' 10 and lter and exhaust for enclosures should be made of stainless steel or some other material which will not contaminate the phosphors. p

While the apparatus for the practice of the present inventionas `described. heretofore issuitable for removing the/:tubezenvelopel into affreceptacle of a multiple posi tion rotary unit (not shown), the envelope 16 then is transported throughathe rotating air massascreemremoval A removed from the unit as a cleaned tube envelope which may then go back into the normal factory tube production routine.

Thus it is apparent that the present invention provides an improved and more economical apparatus for removing uorescent screens from cathode ray tube viewing screen surfaces. Furthermore, the phosphors thus removed are readily salvageable, there is no chemical reaction Which may result in toxic gases being evolved as when acid removal processes are used, and the apparatus, 1

though well adapted for mass production manufacturing techniques, may be used to equal advantage in small scale manufacturing operations.

What is claimed is:

' A nozzle having a body portion provided with a central chamber for receiving a low velocity high pressure gas, said chamber having a longitudinal axis, a plurality of channels' communicating With said central chamber and extending radially therefrom and having their remote ends closed olf, a plurality of non-rotatable restricted .outlet passageways, at least one for each channel, extending from said channels to the outer surface of said body portion in the same circular direction with respect to said axis, said channels and said passageways having their axes substantially normal to each other, each of said plurality of passageways being tangent to a circle drawn with its center substantially at said longitudinal axis and in a plane which is normal to said longitudinal axis, whereby said gas may issue-in high velocity tangential 'ets, and a restricted outlet passagewaycommunicating with said central chamber and substantially parallel with said longitudinal axis. v

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